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991.
Exogenous retinoic acid induces digit reduction in opossums (Monodelphis domestica) by disrupting cell death and proliferation,and apical ectodermal ridge and zone of polarizing activity function
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992.
The DELLA domain of GA INSENSITIVE mediates the interaction with the GA INSENSITIVE DWARF1A gibberellin receptor of Arabidopsis 总被引:6,自引:0,他引:6
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Willige BC Ghosh S Nill C Zourelidou M Dohmann EM Maier A Schwechheimer C 《The Plant cell》2007,19(4):1209-1220
Gibberellic acid (GA) promotes seed germination, elongation growth, and flowering time in plants. GA responses are repressed by DELLA proteins, which contain an N-terminal DELLA domain essential for GA-dependent proteasomal degradation of DELLA repressors. Mutations of or within the DELLA domain of DELLA repressors have been described for species including Arabidopsis thaliana, wheat (Triticum aestivum), maize (Zea mays), and barley (Hordeum vulgare), and we show that these mutations confer GA insensitivity when introduced into the Arabidopsis GA INSENSITIVE (GAI) DELLA repressor. We also demonstrate that Arabidopsis mutants lacking the three GA INSENSITIVE DWARF1 (GID1) GA receptor genes are GA insensitive with respect to GA-promoted growth responses, GA-promoted DELLA repressor degradation, and GA-regulated gene expression. Our genetic interaction studies indicate that GAI and its close homolog REPRESSOR OF ga1-3 are the major growth repressors in a GA receptor mutant background. We further demonstrate that the GA insensitivity of the GAI DELLA domain mutants is explained in all cases by the inability of the mutant proteins to interact with the GID1A GA receptor. Since we found that the GAI DELLA domain alone can mediate GA-dependent GID1A interactions, we propose that the DELLA domain functions as a receiver domain for activated GA receptors. 相似文献
993.
Reischl S Vanselow K Westermark PO Thierfelder N Maier B Herzel H Kramer A 《Journal of biological rhythms》2007,22(5):375-386
Regulated degradation of circadian clock proteins is a crucial step for rhythm generation per se but also for establishing a normal circadian period. Here, the authors show that the F-box protein beta-transducin repeat containing protein 1 (beta-TrCP1) as part of the E3 ubiquitin ligase complex is an essential component of the mammalian circadian oscillator. Down-regulation of endogenous beta-TrCP1 as well as expression of a dominant-negative form both result in lengthening of the circadian period in oscillating fibroblasts. These phenotypes are due to an impaired degradation of PERIOD (PER) proteins, since expression of beta-TrCP interaction-deficient PER2 variants--but not wild-type PER2--results in a dramatic stabilization of PER2 protein as well as in the disruption of circadian rhythmicity. Mathematical modeling conceptualizes the authors' findings and suggests that loss of sustained rhythmicity in cells with eliminated beta-TrCP-mediated PER2 degradation is due to excessive nuclear repression, a prediction they verified experimentally. 相似文献
994.
Helicobacter pylori colonizes the human gastric mucosa and this can lead to chronic gastritis, peptic and duodenal ulcers, and even gastric cancers.
The bacterium colonizes over one-half of the worlds population. Nickel plays a major role in the bacteriums colonization and
persistence attributes as two nickel enzyme sinks obligately contain the metal. Urease accounts for up to 10% of the total
cellular protein made and is required for initial colonization processes, and the hydrogen oxidizing hydrogenase provides
the bacterium a high-energy substrate yielding low potential electrons for energy generation. A battery of accessory proteins
are needed for maturation or activation of each of the apoenzymes. These include Ni-chaperones and GTPases, some of which
are unique to each Ni-enzyme and others that are individually required for maturation of both the Ni-enzymes. H. pylori’s need for some conventional hydrogenase maturation proteins playing roles in urease maturation may have to do with the poor
nickel-sequestering ability of the UreE urease maturation protein compared to other systems. H. pylori also possesses a NixA nickel specific permease, a nickel dependent regulator (NikR), a recently identified nickel efflux
system (CznABC), and a histidine-rich heat shock protein, HspA. Based on mutant analysis approaches all these proteins have
roles in nickel homeostasis, in urease expression, and in host colonization. The His-rich putative nickel storage proteins
Hpn and Hpn-like play roles in nickel detoxification and may influence the levels of Ni-activated urease that can be achieved. 相似文献
995.
Background
Nitrogen, a component of many bio-molecules, is essential for growth and development of all organisms. Most nitrogen exists in the atmosphere, and utilisation of this source is important as a means of avoiding nitrogen starvation. However, the ability to fix atmospheric nitrogen via the nitrogenase enzyme complex is restricted to some bacteria. Eukaryotic organisms are only able to obtain fixed nitrogen through their symbiotic interactions with nitrogen-fixing prokaryotes. These symbioses involve a variety of host organisms, including animals, plants, fungi and protists. 相似文献996.
997.
Fast and efficient baseline separation of asymmetrically substituted diarylmethanols and 1,1-diarylethanols was achieved on an endcapped, amide-linked N-3,5-dinitrobenzoylated, (R, R)-1,2-diphenyl-1,2-ethanediamine-derived chiral stationary phase (CSP). Optimal enantioselectivities on this CSP were obtained using 1% 2-propanol in n-heptane as the mobile phase. Enantiorecognition was found to be governed by π-basicity and the substitution pattern of the aromatic substituents. © 1996 Wiley-Liss, Inc. 相似文献
998.
999.
1000.
Gerhard Maier 《International Review of Hydrobiology》1993,78(1):83-93
Investigations on the life histories of two cladocerans, Moina brachiata and Daphnia obtusa, in a small, nearly temporary pond in South Germany revealed that M. brachiata is better adapted to fluctuating environmental conditions; the species dominated from May to October. D. obtusa was present in spring and autumn/winter but disappeared completely during the summer months. Both species coexisted for extended periods in spring and autumn; abundance of D. obtusa was generally by an order of magnitute lower. Four periods of low water level were slightly preceded by or coincided with a decrease of clutch size, a decrease of the proportion of egg bearing females indicating that both species suffered from food shortage. Laboratory investigations on life history parameters showed that the two species have different temperature tolerances and preferences. M. brachiata showed its highest reproductive success at 25 and 30°C but died at temperatures <15°C and ≥ 35°C. D. obtusa experienced a broader temperature range (2 to 25°C) but could not withstand temperatures ≥ 30°C. Short term starvation periods (3d) caused the death of M. brachiata females, while D. obtusa soon recovered and reproduced when being refed. M. brachiata is a typical r-species with early reproduction, rapid development, high population growth rates and a high tendency to produce resting eggs; D. obtusa pursues more the concept of k-selection. 相似文献